Analogue is defined as quantities that change continuously in time. The change of the corresponding quantity can occur over time
or over another physical quantity. Functional is the continuous representation of one physical quantity (y) in relation to a second (x). If the second physical quantity is time, the change is said to be continuous in time.
As examples, voltage change is generally a time-dependent analog signal, but it can also be a pressure change over temperature or a field strength change over distance. In contrast to analog values are digital
values. The comparisons between analog and digital representation generally refer to the pointer display of an instrument, the tachometer or the clock and the digit representation of the corresponding instruments.